[llvm] r303774 - [InstSimplify] Simplify uadd/sadd/umul/smul with overflow intrinsics when the Zero or Undef is on the LHS.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Wed May 24 12:05:28 2017
New Revision: 303774

URL: http://llvm.org/viewvc/llvm-project?rev=303774&view=rev
Log:
[InstSimplify] Simplify uadd/sadd/umul/smul with overflow intrinsics when the Zero or Undef is on the LHS.

Summary: This code was migrated from InstCombine a few years ago. InstCombine had nearby code that would move Constants to the RHS for these, but InstSimplify doesn't have such code on this path.

Reviewers: spatel, majnemer, davide

Reviewed By: spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33473

Modified:
    llvm/trunk/lib/Analysis/InstructionSimplify.cpp
    llvm/trunk/test/Transforms/InstSimplify/call.ll

Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=303774&r1=303773&r2=303774&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Wed May 24 12:05:28 2017
@@ -4440,19 +4440,21 @@ static Value *SimplifyIntrinsic(Function
     case Intrinsic::uadd_with_overflow:
     case Intrinsic::sadd_with_overflow: {
       // X + undef -> undef
-      if (isa<UndefValue>(RHS))
+      if (isa<UndefValue>(LHS) || isa<UndefValue>(RHS))
         return UndefValue::get(ReturnType);
 
       return nullptr;
     }
     case Intrinsic::umul_with_overflow:
     case Intrinsic::smul_with_overflow: {
+      // 0 * X -> { 0, false }
       // X * 0 -> { 0, false }
-      if (match(RHS, m_Zero()))
+      if (match(LHS, m_Zero()) || match(RHS, m_Zero()))
         return Constant::getNullValue(ReturnType);
 
+      // undef * X -> { 0, false }
       // X * undef -> { 0, false }
-      if (match(RHS, m_Undef()))
+      if (match(LHS, m_Undef()) || match(RHS, m_Undef()))
         return Constant::getNullValue(ReturnType);
 
       return nullptr;

Modified: llvm/trunk/test/Transforms/InstSimplify/call.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/call.ll?rev=303774&r1=303773&r2=303774&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/call.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/call.ll Wed May 24 12:05:28 2017
@@ -35,6 +35,14 @@ define {i8, i1} @test_uadd3(i8 %v) {
   ret {i8, i1} %result
 }
 
+define {i8, i1} @test_uadd4(i8 %v) {
+; CHECK-LABEL: @test_uadd4(
+; CHECK-NEXT:    ret { i8, i1 } undef
+;
+  %result = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 undef, i8 %v)
+  ret {i8, i1} %result
+}
+
 define i1 @test_sadd1() {
 ; CHECK-LABEL: @test_sadd1(
 ; CHECK-NEXT:    ret i1 true
@@ -61,6 +69,14 @@ define {i8, i1} @test_sadd3(i8 %v) {
   ret {i8, i1} %result
 }
 
+define {i8, i1} @test_sadd4(i8 %v) {
+; CHECK-LABEL: @test_sadd4(
+; CHECK-NEXT:    ret { i8, i1 } undef
+;
+  %result = call {i8, i1} @llvm.sadd.with.overflow.i8(i8 undef, i8 %v)
+  ret {i8, i1} %result
+}
+
 define {i8, i1} @test_usub1(i8 %V) {
 ; CHECK-LABEL: @test_usub1(
 ; CHECK-NEXT:    ret { i8, i1 } zeroinitializer
@@ -125,6 +141,22 @@ define {i8, i1} @test_umul2(i8 %V) {
   ret {i8, i1} %x
 }
 
+define {i8, i1} @test_umul3(i8 %V) {
+; CHECK-LABEL: @test_umul3(
+; CHECK-NEXT:    ret { i8, i1 } zeroinitializer
+;
+  %x = call {i8, i1} @llvm.umul.with.overflow.i8(i8 0, i8 %V)
+  ret {i8, i1} %x
+}
+
+define {i8, i1} @test_umul4(i8 %V) {
+; CHECK-LABEL: @test_umul4(
+; CHECK-NEXT:    ret { i8, i1 } zeroinitializer
+;
+  %x = call {i8, i1} @llvm.umul.with.overflow.i8(i8 undef, i8 %V)
+  ret {i8, i1} %x
+}
+
 define {i8, i1} @test_smul1(i8 %V) {
 ; CHECK-LABEL: @test_smul1(
 ; CHECK-NEXT:    ret { i8, i1 } zeroinitializer
@@ -141,6 +173,22 @@ define {i8, i1} @test_smul2(i8 %V) {
   ret {i8, i1} %x
 }
 
+define {i8, i1} @test_smul3(i8 %V) {
+; CHECK-LABEL: @test_smul3(
+; CHECK-NEXT:    ret { i8, i1 } zeroinitializer
+;
+  %x = call {i8, i1} @llvm.smul.with.overflow.i8(i8 0, i8 %V)
+  ret {i8, i1} %x
+}
+
+define {i8, i1} @test_smul4(i8 %V) {
+; CHECK-LABEL: @test_smul4(
+; CHECK-NEXT:    ret { i8, i1 } zeroinitializer
+;
+  %x = call {i8, i1} @llvm.smul.with.overflow.i8(i8 undef, i8 %V)
+  ret {i8, i1} %x
+}
+
 declare i256 @llvm.cttz.i256(i256 %src, i1 %is_zero_undef)
 
 define i256 @test_cttz() {